Bootnodes update

Moved database update loop to eth/backend

Add block header validations for block tests

Update pub key for EU node and add new SA node

change order of block insert and update LastBlock

bugfix, wrong hash stored in blockDb

doc: crypto/secp256k1 GMP dependency package name.

Linux build documentation is mostly geared towards Ubuntu 14.04 (LTS).
Appropriate package is called `libgmp-dev` there.

Note that on pristine installations building `geth` with godep will
fail because this header is missing. This is not documented in the
top-level README, but is on the wiki:

https://github.com/ethereum/go-ethereum/wiki/Installation-Instructions-for-Ubuntu#building-geth-command-line-client

That page recommends `libgmp3-dev`, which ATM provides same version
as `libgmp-dev`.

core: transaction queue

Transactions are now propagated to peers from which we have not yet
received the transaction. This will significantly reduce the chatter on
the network.

Moved new mined block handler to the protocol handler and moved
transaction handling to protocol handler.

Set the state for the managed tx state instead of creating a new
managed state.

Implemented a new transaction queue. Transactions with a holes in their
nonce sequence are also not propagated over the network.

N: 0,1,2,5,6,7 = propagate 0..2 -- 5..N is kept in the tx pool

Block tests reloaded

Adding flags to facilitate cross compiling to ARM

Empty Call response should return 0x instead of 0x00. Closes #739

Changed "Welcome to the Frontier" to something more geeky